Not many places I have worked for allowed for this to be automatic. A lot of it was so they could provide a coherent explanation as to what the current state of internal attention was directed at vs what everyone can plainly see.
I guess this makes sense, but I don't understand why you couldn't have it change status automatically, and still allow a person to go in after and manually add an explanation.
Mostly because it's more work to manually remove a bunch of spurious robotically added statuses (which look bad, because you're either down more than customers are noticing or your detection is flawed) than it is to manually add and remove real ones.
I think it is so they can "hide" small outages that don't rise to the level of making the news sites so they can look better. A lot of sites do this sort of thing these days.
When I worked at GCP it was all manually updated as well so we could add a sentence about what was actually affected. In any sufficiently large system it's hard to indicate exactly what's broken/how to work around it, so it was just easier to `/status <system> <color> <reason for status>`.